Eastern Pacific Tropical Weather Discussion

000
AXPZ20 KNHC 311547
TWDEP
TROPICAL WEATHER DISCUSSION...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE MAR 31 2015
CORRECTED FOR DISCUSSION INFORMATION
TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.
BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1500 UTC.
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE ITCZ AXIS EXTENDS FROM 05N120W TO 07N126W TO BEYOND 05N140W.
A SECOND AND WELL DEFINED ITCZ AXIS IS NOTED SOUTH OF THE
EQUATOR FROM 03.4S90W TO 02S100W TO 3.4S110W. SCATTERED MODERATE
CONVECTION IS S OF THE EQUATOR BETWEEN 92W AND 104W. SIMILAR
CONVECTION IS ALSO OBSERVED FROM 05N TO 10N BETWEEN 120W AND
128W...AND FROM 05N TO 08N BETWEEN 117W AND 119W.
DURING MARCH AND APRIL...THE MONSOONAL CIRCULATION OVER THE
TROPICAL NE PACIFIC IS NOT PRESENT...AND OCCASIONALLY BREAKS
DOWN WITH CONVERGENCE NOTED ON EACH SIDE OF THE EQUATOR IN WHAT
IS REFERRED TO AS A DOUBLE ITCZ STRUCTURE. AS PREVIOUSLY
MENTIONED A SECOND ITCZ IS SEEN S OF THE EQUATOR ON THE 1200 UTC
SURFACE MAP. THE PRESENCE OF AN ACTIVE SOUTHERN ITCZ IS FORECAST
TO PERSIST OVER THE NEXT 24-48 HOURS.
...DISCUSSION...
A RIDGE COVERS THE NORTHERN WATERS MAINLY N OF 17N W OF 118W.
SOUTH OF THE RIDGE...THE PRES GRADIENT BETWEEN THE HIGH AND
LOWER PRES ALONG THE ITCZ IS RESULTING IN FRESH NE TRADEWINDS
FROM 14N TO 18N W OF 135W...WHERE SEAS ARE 8-9 FT IN MIXED NE
AND NW SWELL. A DISSIPATING FRONTAL BOUNDARY IS CLIPPING THE FAR
NW CORNER OF THE AREA AND CURRENTLY EXTENDS FROM 30N135W TO
BEYOND 28N140W. STRONGER HIGH PRES IN THE WAKE OF THE FRONT
MOVING EASTWARD WILL THEN DOMINATE THE NORTHERN FORECAST WATERS
OVER THE NEXT COUPLE OF DAYS. THIS WILL BRING AN INCREASE IN
NORTHERLY WINDS AND SEAS BY THIS EVENING AS PRES GRADIENT
TIGHTENS BETWEEN THE HIGH AND LOWER PRES ACROSS SOUTHWESTERN
UNITED STATES AND NW MEXICO. IN FACT...GALE FORCE WINDS ARE
FORECAST TO DEVELOP JUST N OF AREA AND E OF 128W. UNDER THE
INFLUENCE OF THIS WEATHER PATTERN...EXPECT FRESH TO STRONG
NORTHERLY WINDS MAINLY N OF 27N BETWEEN 118W AND 130W WITH SEAS
BUILDING TO 12 FT PRIMARILY IN NW SWELL THIS EVENING INTO WED.
NWP GUIDANCE SUGGESTS THAT FRESH NE-E WINDS WILL BLOW ACROSS
MOST OF THE WATERS N OF 20N W OF 120W BY WED NIGHT. ADDITIONAL
PULSES OF NW SWELL CONTINUE TO REACH THE NW PART OF THE FORECAST
REGION AND WILL MIX WITH NE WIND WAVES TO BUILD SEAS TO 9 FT W
OF LINE FROM 30N116W TO 24N120W TO 20N130W TO 09N135W BY WED
MORNING.
A STATIONARY TROUGH IS ANALYZED ON THE 1200 UTC SURFACE MAP FROM
14N114W TO 09N115W. ISOLATED MODERATE CONVECTION IS SEEN ON
SATELLITE IMAGERY NEAR THE TROUGH AXIS. THIS TROUGH WILL DRIFT
WESTWARD.
WITH THE EXCEPTION OF THE GAP WIND REGIONS...MAINLY LIGHT TO
GENTLE WINDS PREVAIL ACROSS MOST OF THE AREA E OF 110W. LONG
PERIOD SOUTHERLY SWELL CONTINUES TO FADE ACROSS MUCH OF THIS
REGION WITH SEAS GENERALLY 5-7 FT. ANOTHER BATCH OF CROSS
EQUATORIAL SOUTHERLY SWELL WILL SPREAD ACROSS THE SOUTH WATERS
TODAY AND COULD REACH THE COASTS OF CENTRAL AMERICA AND MEXICO
BY LATE THU.
GAP WINDS...
GULF OF TEHUANTEPEC...A HIGH RESOLUTION RAPIDSCAT FROM 1200 UTC
PROVIDED OBSERVATIONS OF NORTHERLY WINDS IN THE 20-30 KT RANGE
ACROSS THE GULF OF TEHUANTEPEC AND DOWNWIND TO NEAR 14N95W. THE
WINDS ARE EXPECTED TO DROP BELOW 20 KT BY THIS EVENING.
CLIMATOLOGICALLY...THE FINAL GALE FORCE WIND EVENT OCCURS IN THE
GULF OF TEHUANTEPEC IN LATE MARCH OR EARLY APRIL.
GULF OF PAPAGAYO...THE SAME SCATTEROMETER PASS OBSERVED FRESH TO
STRONG NE WINDS ACROSS THE GULF OF PAPAGAY0 AND DOWNWIND TO NEAR
09N89W. PULSING OF NOCTURNAL WINDS ARE EXPECTED ACROSS THE GULF
OF PAPAGAYO THROUGH THU MORNING...REACHING 20-25 KT FROM 0600 TO
1200 UTC...WITH SEAS OF 6-7 FT THROUGH AND DOWNWIND OF THE GULF.
$$
GR